1. Field of the Invention
Rope hoists have an essentially cylindrical rope drum, which is rotatably mounted in a frame. The rope drum is driven by means of a geared motor, the output shaft of the gearing being coupled to the rope drum in a rotationally locked manner. During the manufacture of the frame, alignment errors, in accordance with the manufacturing tolerances, are to be expected between the bearing seats for mounting the drum and the fastening points for the geared motor. So that these tolerances do not lead to distortions in the drive, a shaft coupling which can absorb these alignment errors has been used in the past between the output shaft and the rope drum. A disadvantage in this case is the high production and assembly cost resulting from the shaft coupling and the fact that essentially three bearings are required, namely two bearings for mounting the drum and a bearing device for mounting the output shaft of the gearing.
2. Description of the Related Art
It has therefore been attempted to restrict the number of bearings or to change their position, inter alia with the aim of dispensing with the shaft coupling between the rope drum and the output shaft of the gearing. However, the rope drum on the gearing side may then no longer be mounted in a bearing accommodated in the frame. On the contrary, the bearing must become part of the gearbox, so that, with small tolerances, it is in alignment with the bearing of the output shaft. DE 37 43 889 C2 discloses such a design. In the rope hoist described there, the gearbox is provided with a bearing seat for accommodating a bearing on which one end of the rope drum is directly mounted. The gearing in turn is fastened to the frame. As a result of this arrangement, alignment problems may now occur between the two rope-drum bearings, since one of the bearings is formed directly in the frame, whereas the other is part of the geared motor. In order to cope with the distortions which unavoidably occur as a result, the fastening of the gearing to the frame is of elastic design. In addition, that end of the rope drum which is remote from the gearing is likewise mounted in the frame via elastic elements.
The cost of this is relatively high.
A somewhat different method is adopted in the rope hoist according to FR 1 458 160 A1. In this solution, the frame for mounting the rope drum has half pillow blocks, which are open at the top and in which ball bearings are inserted. An elastic compliant layer is located between the ball bearing and the bearing seat in the pillow block. The rope drum is provided with one-piece end disks, a bearing journal being inserted into each of them. One of the bearing journals is at the same time the output shaft of the gearing of the geared motor.
On account of this design, the gearing and the geared motor are carried by the output shaft, which is mounted in one of the drum pillow blocks. This solution, too, does not reduce the number of bearings for mounting the output shaft and the rope drum.
This additional bearing is dispensed with in the rope hoist according to DE-B 1 205 247. In the known arrangement, the drive motor for driving the rope drum sits inside the rope drum. For this purpose, the rope drum has a recess at one end, and an annular end plate is inserted into this recess. The bore of the end plate constitutes a bearing seat for a ball bearing, with which the rope drum is rotatably mounted on a tubular extension of the motor casing. The tubular extension of the motor arranged in the rope drum leads out of the rope drum and is screwed outside the rope drum to a flange plate. In addition, the armature shaft of the motor projects from the rope drum, so that the armature shaft can be connected to a brake device on the other side of the flange plate.
Inside the rope drum, the motor casing is actually overhung and is supported at the end lying inside the rope drum only by the armature shaft, which is rotatably mounted with a needle bearing in the output shaft of the gearing, the output shaft projecting into the rope drum. Likewise located coaxially inside the output shaft of the gearing is the gearing input shaft, which is connected in a rotationally locked manner to gears outside the rope drum. The output shaft and thus also the input shaft mounted in the output shaft are mounted in a tubular extension of the gearbox, which projects into the rope drum.
The output shaft is in one piece with a radially extending flange, which is screwed to an annular web located inside the rope drum.
On account of this arrangement, the rope drum, the motor and the gearing form a self-contained, self-supporting unit, which no longer requires further outer frames for the purpose of positioning the individual shaft bearings and fastening them in the correct position. In the known design, the rope drum forms the actual frame, on which all the rolling-contact bearings of the arrangement are supported indirectly or directly. The additional yoke, which overlaps on both sides of the rope drum and is connected at one end to the flange plate, on which the motor casing is mounted, and which is fastened at the other end to the tubular extension of the gearbox, merely constitutes a device which is necessary in order to be able to suspend the rope hoist on a supporting framework. Bearing forces are not transmitted in this respect.
Since the rope drum is the actual frame of the rope hoist, the rope drum and also all the other bearing devices must be machined to a very high accuracy, so that the alignment errors of the parts rotating relative to one another are as small as possible. Otherwise, large bearing forces would be produced on account of the rigidity of the rope drum, and these bearing forces would quickly lead to the destruction of the bearings.
Against this background, the object of the invention is to provide a rope hoist in which the gearing-side mounting of the rope drum is effected solely via the output shaft and in which no great demands are made on the production accuracy of the frame.
This object is achieved according to the invention with the rope hoist having the features of claim 1.
Compared with the rigid design of the frame, the torsionally nonrigid, elastic frame reduces the distortion forces which occur if the axes of the bearings of the rope drum are laterally offset from one another, that is, have lateral runout, and also reduces the forces which are produced if one or both bearing journals exhibit wobbling runout. In a torsionally rigid frame, these design errors would lead to forces which would immediately destroy the rolling-contact bearings. This is not the situation in the case of the compliant frame. Furthermore, in the case of the compliant frame, the additional fastening means for the gearing which are disclosed by the prior art are unnecessary, as a result of which the fastening of the gearing to the frame is substantially simplified.
It was surprising in this case that the compliant frame, i.e. the frame which is no longer torsionally rigid, is nonetheless able to absorb the forces which occur when the maximum load in accordance with the intended use hangs on the rope of the rope hoist.
Furthermore, a simplification becomes apparent by virtue of the fact that the mounting of the output shaft of the gearing is used as one of the two drum bearings. Alignment problems between the gearing-side drum mounting and the mounting of the output shaft thus do not occur, and no countermeasures have to be taken in order to cope with possible alignment errors. Thus the configuration of the entire construction is thereby also substantially simplified.
In particular, the novel design of the rope hoist is suitable for use in combination with a crab carriage, the frame for mounting the rope drum representing a cheek of the crab carriage.
Especially favorable forces or compliance ratios of the frame are obtained if the frame-base means has a roughly C-shaped configuration as viewed from the position of the rope drum. This C-shaped configuration can be achieved if the frame-base means has a longitudinal member extending parallel to the rope drum. Elongated head pieces may be welded to this longitudinal member. The head pieces are elongated structures, which run transversely to the longitudinal member, preferably vertically in the operating position of the rope hoist.
A favorable ratio between strength and mass is achieved if the longitudinal member and/or the head pieces are tubular, preferably having a square cross section.
Good compliance of the frame in the face of distortion forces as a result of alignment errors of the bearing journals of the rope drum on the one hand and sufficient strength in the face of forces which are caused by the load hanging on the rope are achieved if the frame, in plan view, has a roughly C-shaped configuration, which is defined by the frame-head means and the frame-base means. In the case of a C-shaped configuration, the frame-head means can be moved relatively easily at an angle to one another, specifically in the sense of a bending load on the frame-base means, if the axes of the two bearing journals enclose an angle with one another which is different from 180xc2x0. In the case of such an alignment error, the frame-base means would be periodically stressed in bending. Vertical offset of the journals, however, would lead to torsion of the frame-base means.
Compliance is promoted if the frame-head means to which the gearing is fastened and/or the frame-head means to which the other bearing, i.e. the drum bearing arrangement, is fastened, has an essentially platelike configuration.
An even greater degree of elasticity of the frame and easier assembly are achieved if at least one of the frame-head means, preferably the frame-head means connected to the gearing, is bifurcated with the formation of two legs. In this arrangement, the output shaft passes through between the two legs of the frame-head means.
Since, in the novel embodiment, tumbling forces or tumbling movements are deliberately tolerated for the frame, provision must be made for especially reliable fastening of the gearing to the relevant frame-head means. Such especially reliable fastening is achieved if pairs of holes in alignment with one another are contained in the frame-head means and the gearbox, a flanged bush fitting in each pair of holes. The shearing forces caused by the attachment are thus transmitted via the flanged bush, whereas a screw leading through the flanged bush is free of shearing forces and merely transmits tensile forces.
The assembly of the novel rope hoist is simplified if the output shaft is provided with a one-piece flange plate, which fits into a corresponding locating seat of the rope drum. The motor gearing unit can thereby be manufactured and dispatched as a preassembled unit.
An especially simple assembly of the output shaft is achieved in the novel rope hoist if the output gear, which sits on the output shaft, is profile-interlocked with the latter.
With its frame, the novel rope hoist may be part of a complete crab carriage, the frame constituting a cheek of the carriage.
In addition, developments of the invention are the subject matter of subclaims.